Fluoropolymer binder

Abstract

The present invention relates generally to the field of electrical energy storage in secondary batteries of Li-ion type. More specifically, the invention relates to a binder in the form of a powder based on a homogeneous mixture of fluoropolymers. The invention also relates to a number of processes for preparing said binder. Lastly, the invention relates to an electrode comprising said binder, and also to Li-ion secondary batteries comprising at least one such electrode.

1 . A lithium-ion battery binder consisting of a mixture of a polytetrafluoroethylene (PTFE) phase formed from primary particles of PTFE having a size ranging from 10 nm to 1 μm and a polyvinylidene fluoride (PVDF) phase formed from primary particles of PVDF having a size ranging from 10 nm to 1 μm, said binder being in the form of a powder. 
     
     
         2 . The lithium-ion battery binder of  claim 1 , wherein the PTFE particles have a size ranging from 50 nm to 500 nm. 
     
     
         3 . The lithium-ion battery binder of  claim 1 , wherein the PVDF particles have a size ranging from 50 nm to 500 nm. 
     
     
         4 . The lithium-ion battery binder of  claim 1 , wherein the PVDF is selected from polyvinylidene fluoride homopolymers or copolymers of vinylidene difluoride with at least one comonomer selected from the group consisting of: vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropene, 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, 1,1,3,3,3-pentafluoropropene, 1,2,3,3,3-pentafluoropropene, perfluoro(propyl vinyl ether), perfluoro(methyl vinyl ether), bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, chlorotrifluoropropene, ethylene and mixtures thereof. 
     
     
         5 . A process for producing the binder of  claim 1 , comprising said process comprising the following steps:
 a. mixing a PVDF latex with a PTFE latex to form a PVDF latex/PTFE latex mixture,   b. adding water to the PVDF latex/PTFE latex mixture to bring the polymer content of to between 10% and 50% by weight,   c. co-spraying the PVDF latex/PTFE latex mixture obtained in step b to obtain a composite powder formed from particles of PTFE and particles of PVDF.   
     
     
         6 . A process for producing the binder according to  claim 1 , by polymerization of PVDF in the presence of a seeding of PTFE. 
     
     
         7 . A process for producing the binder according to  claim 1 , by polymerization of PTFE in the presence of a seeding of PVDF. 
     
     
         8 . A Li-ion battery electrode comprising an active filler for anode or cathode, an electrically conductive filler and the lithium-ion battery binder of  claim 1 . 
     
     
         9 . The Li-ion battery electrode of  claim 8 , wherein the electrode is a negative electrode, wherein said active filler is selected from lithium metal, graphite, silicon/carbon composites, silicon, graphene, fluorographites of CFx type where x is between 0 and 1, and titanates of LiTi 5 O 12  type. 
     
     
         10 . The Li-ion battery electrode of to  claim 8 , wherein the electrode is a positive electrode, wherein said active filler is selected from active materials of the LiMO 2  type, of the LiMPO 4  type, of the Li 2 MPO 3 F type, of the Li 2 MSiO 4  type where M is Co, Ni, Mn, Fe or a combination of these, of the LiMn 2 O 4  type, of the S 8  type or of the lithium polysulfide type represented by the formula Li 2 S n  where n>1; for a positive electrode. 
     
     
         11 . The Li-ion battery electrode of  claim 8 , wherein the conductive fillers are selected from the group consisting of carbon blacks, natural or synthetic graphites, carbon fibres, carbon nanotubes, metal fibres and powders, conductive metal oxides or mixtures thereof. 
     
     
         12 . The Li-ion battery electrode of  claim 8  having the following composition by mass:
 50% to 99% of active filler 
 25% to 0.05% of conductive filler, 
 10% to 0.5% of polymeric binder, 
 0% to 5% of at least one additive selected from the group consisting of: plasticizer, ionic liquid, dispersant for the conductive fillers and flow agent for the formulation, 
 
       the sum of all these percentages being 100%. 
     
     
         13 . A process for producing the Li-ion battery electrode of  claim 8 , said process comprising the steps of:
 mixing the active filler, the polymeric binder and the conductive filler by means of a process that makes it possible to obtain an electrode formulation that can be applied to a metal support by a solvent-free process;   depositing said electrode formulation on the metal substrate by a solvent-free process so as to obtain a Li-ion battery electrode and   consolidating said electrode by a heat treatment and/or thermomechanical treatment.   
     
     
         14 . A secondary Li-ion battery comprising an anode, a cathode and a separator, wherein at least one of the electrodes comprises the Li-ion battery electrode of  claim 8 . 
     
     
         15 . A supercapacitor comprising at least one electrode according to  claim 8 .